Battery charging system with reverse battery protection

ABSTRACT

A circuit prevents a generating machine from being operatively connected to a battery whenever the battery has been connected with a reverse polarity. The machine is coupled through the anode-cathode path of a silicon-controlled rectifier to the battery and the rectifier is switched on in response to current pulses in the field winding of the machine. A primary winding of a pulse transformer and the secondary winding of the pulse transformer are employed to supply gating pulses to the controlled rectifier. The transformer has a saturating winding which is energized when the battery is connected in a reverse direction so that no gating pulses are coupled through the transformer to the gate of the controlled rectifier to turn on the controlled rectifier.

United States Patent 15] 3,659,182 Snedeker 5] Apr. 25, 1972 [54]BATTERY CHARGING SYSTEM WITH REVERSE BATTERY PROTECTION Inventor:

Assignee:

Filed:

Appl.

Sept. 3, 1970 Int. Cl.

References Cited Marion L. Snedeker, Cleveland, Ohio VLN Corporation,Cleveland, Ohio UNITED STATES PATENTS u.s. Cl "7.320125, 307/127 ..H02j7/00 Field of Search .307/127, 314; 320/25, 26

3,524,078 8/1970 Harris ..307/3 1 4 X Primary Examiner-William M. Shoop,Jr. Attorney-Yount & Tarolli [5 7] ABSTRACT A circuit prevents agenerating machine from being operatively connected to a batterywhenever the battery has been connected with a reverse polarity. Themachine is coupled through the anode-cathode path of asilicon-controlled rectifier to the battery and the rectifier isswitched on in response to current pulses in the field winding of themachine. A primary winding of a pulse transformer and the secondarywinding of the pulse transformer are employed to supply gating pulses tothe controlled rectifier. The transformer has a saturating winding whichis energized when the battery is connected in a reverse direction sothat no gating pulses are coupled through the transformer to the gate ofthe controlled rectifier to turn on the controlled rectifier.

15 Claims, 1 Drawing Figure BATTERY CHARGING SYSTEM WITH REVERSE BATTERYPROTECTION Automotive or other storage batteries charged from agenerating machine may be inadvertently connected with a reversepolarity.

It is an object of the present invention to provide a new and improvedpolarity reversal protective circuit in which a generating machine isconnected to a battery through a gate device which is activated directlyin response to current pulses in the field of the machine.

Another object of the present invention is to provide a new and improvedelectrical circuit for operatively connecting a voltage generator meanshaving a field winding with a DC. voltage source in which the fieldcurrent in the generator means is sensed and used to control theconnection of the voltage generating means to the DC. voltage source andin which the field current is rendered ineffective to effect theconnection of the generating machine to the battery with a reversedbattery.

A further object of the present invention is to provide a new andimproved control system for connecting a generating machine to a batteryto be charged in which signals are normally transmitted by a transformerto connect the output of the machine to the battery when the machinestarts operating, the transformer being saturated in the event thebattery is inserted with reverse polarity to prevent connection of thegenerating machine to the battery.

Other objects and advantages of the present invention will be apparentfrom the following description and the drawing.

The FIGURE is a schematic representation of a specific embodiment of thepreferred circuit arrangement embodying the present invention.

ln the illustrated embodiment, a direct current generator having a fieldwinding 26 is employed to charge a battery 12. A regulator including avoltage sensing circuit 14 and an output transistor 18 is utilized tocontrol the current in the field circuit of the generator 10 to providea substantially constant voltage to the battery 12. The regulator is aconventional transistorized regulator circuit which supplies a signal tothe base of the PNP transistor 18 to switch the transistor off and on asthe generator output voltage rises and falls to predeter mined levels toturn the field current for the generator on and off to maintain asubstantially constant output voltage from the generator. The fieldcircuit is through the collectoremitter path of the transistor 18 andincludes a diode 20, the primary winding 22 of a transformer 24, and afield winding 26 of the generator 10. During normal operation, the fieldcurrent is switched on and off at a relatively rapid rate. A diode 28which is coupled across the primary winding 22 of the transformer 24 anda diode 30 which is coupled across the field winding 26 of the generator10 are free wheeling or field discharge diodes and act to shunt theirrespective windings when the transistor 18 is turned off and therespective magnetic fields in the windings collapse. A resistor 32 isconnected in the circuit between the primary winding 22 of thetransformer 24 and the normally negative side of the system. Resistor 32limits the magnitude of current flowing through winding 22 to a safevalue.

A controlled rectifier 34, which preferably is a silicon-controlledrecitfier, has its anode-cathode path coupled between the positiveterminal of the battery 12 and the positive output terminal of thegenerator 10 and functions as a switch for preventing reverse batterycurrent when the generator is not operating or operating at a lowvoltage output. The gate of the silicon-controlled rectifier 34 controlsthe operation of the switch and the gate-cathode circuit of SCR 34 isconnected in a series circuit with the secondary winding 36 oftransformer 24. When the battery 12 is connected with the correctpolarity, as shown in the figure, pulses in the field circuit inducegating pulses in the secondary winding 36 of the transformer 24 to applypositive pulses between the gate and cathode of the SCR 34. Thus, thegate will be rendered positive with respect to the cathode of SCR 34 andthe pulses will render the SCR 34 conductive when the generator 10 isoperating and current pulses are established in the field. The SCR willnot be turned on by the pulses until the output of the generator is highenough to render the anode of the SCR positive with respect to thecathode. A pair of diodes 38 and 40 are associated with the gate of theSCR 34 and winding 36 so that positive voltage pulses are coupled to thegate of the SCR 34 through diode 38 and negative pulses are shorted bythe diode 40.

The primary winding 22 and the secondary winding 36 of the transformer24 and the third winding, or control winding 42, are all wound on thesame transformer core. When the battery 12 is connected with a polarityshown in the figure, the diode 44 which has its cathode connected to thepositive terminal of the battery 12 will be reverse biased and nocurrent will flow through the diode 44, the resistor 46 or the controlwinding 42. Thus, the control pulses which are supplied by thetransistor 18 to the primary winding 22 of the transformer 24 will becoupled through the secondary winding 36 of the transformer 24 wherethey will be supplied as gating pulses to the gate of the controlledrectifier 34.

When the battery 12 is connected in the reverse direction with itsnegative terminal connected to the cathode of the controlled rectifier34, the diode 44 will be forward biased and current will flow throughthe control winding 42, the resistor 46 and the diode 44. The currentmagnitude may be controlled by the value of the resistor 46 so that thecore of the transformer 24 on which the windings 22, 36 and 42 are allwound will be saturated. When the core of the transformer 24 issaturated, control pulses from the transistor 18 will no longer becoupled from the primary winding 22 to the secondary winding 36 of thetransformer 24 and the controlled rectifier 34 cannot be gated on. Whenthe core of the transformer 24 is saturated, no voltage will be inducedinto the secondary winding 36 by the field current. Thus, gating pulsesof the proper polarity will not be applied to the SCR 34 and the SCR 34will not conduct. When the SCR 34 does not conduct, the generator 10will be essentially isolated from the battery 12 and no destructivecurrent will flow from the battery to the generator 10.

From the foregoing, it should be apparent that a new and improvedcircuitry has been provided to prevent a generating machine from beingoperatively connected with the battery when the polarity of the batteryis reversed. Although the present invention has been described withreference to a particular embodiment, it will be obvious to thoseskilled in the art that various other modifications, such as thereplacement of the generator with an alternator, may be employed in thescope of the present invention.

What is claimed is:

1. In a generating system comprising a generating machine including afield circuit comprising a field winding and electrical connections forconnecting a battery to be charged by said generating machine to saidmachine, said connections including switching means having first andsecond conditions for respectively electrically connecting anddisconnecting said generating machine to and from said battery, saidswitching means requiring a predetermined electrical signal foractuation from its first condition to its second condition, second meansfor providing said electrical signal when said generating machine isgenerating an output comprising a transformer having a primary windingconnected to said generating machine to be energized with a currentwhich changes in a pulsing manner when said generating machine isoperating and a secondary winding connected to said switching means toprovide said predetermined signal in response to a predetermined pulsingchange in said current, and third means responsive to reverse batterypolarity for saturating said transformer to prevent current in saidprimary winding from inducing currents in said secondary winding toprovide said predetermined signal.

2. In a generating system as defined in claim 1 wherein said generatingmachine is a machine which generates a direct current.

3. In a generating system as defined in claim 16 wherein said primarywinding is connected into the field circuit of said generating machine.

4. In a generating system as defined in claim 3 wherein said switchingmeans is a controlled rectifier and said secondary winding is connectedto provide gate signals to said rectifier.

5. In a generating system as defined in claim 3 wherein said systemincludes a voltage regulator for regulating the output of saidgenerating machine by controlling the current in said field winding inresponse to said output, said regulating means switching off and on asthe output of said generating machine rises and falls to predeterminedlevels to provide said current which pulses in a predetermined manner.

6. In a generating system as defined in claim 4 wherein said systemincludes a voltage regulator for regulating the output of saidgenerating machine by controlling the current in said field winding inresponse to said output, said regulating means switching off and on asthe output of said generating machine rises and falls to predeterminedlevels to provide said current which pulses in a predetermined manner.

7. In a generating system as defined in claim 1 wherein said third meanscomprises a saturating winding for said transformer and circuit meansconnecting said saturating winding across the battery terminals of saidbattery, said circuit means including uni-directional conducting meansfor blocking currentflow in said saturating winding when said battery isconnected to the battery terminals with proper polarity and whereby saidcircuit means is conductive when said battery is inserted with reversepolarity to saturate said transformer.

8. In a generating system as defined in claim 7 wherein said switchingmeans is a controlled rectifier and said secondary winding is connectedto provide gate signals to said rectifier.

9. In a generating system as defined in claim 7 wherein said machine isa generating machine for generating a direct current and said primarywinding is connected into the field circuit ofsaid generating machine.

10. In a generating system as defined in claim 9 wherein said switchingmeans is a controlled rectifier and said secondary winding is connectedto provide gate signals to said rectifier.

11. In a generating system as defined in claim 9 wherein said generatingsystem includes voltage regulating machine responsive to the output ofsaid generating means for controlling the field current in said fieldwinding, said voltage regulating means switching said field current offand on as the output of said generating machine rises and falls topredetermined levels to provide said current which pulses in apredetermined manner.

12. In a generating system, generating means to be connected to supplydirect current to charge a battery, said generating means having a fieldcircuit comprising a field winding, load conductors connecting theoutput of said generating means to said battery, switching means in saidload conductors for connecting and disconnecting the output of saidgenerating means to and from said battery, means for sensing current insaid field circuit, and means responsive to the last said means forsupplying a signal to said switching means to activate the latter toconnect the generating means to said battery when the generating meanshas started.

13. In a generating system as defined in claim 12 wherein said means forsensing current in said field circuit comprises a circuit elementconnected in series with said field winding.

14. In a generating system as defined in claim 12 in which saidgenerating system includes means responsive to the polarity of saidbattery for inhibiting the activation of said switching means inresponse to said means for sensing current in said field.

15. In a generating system as defined in claim 14 wherein said switchingmeans comprises a controlled rectifier having its anode connected to thepositive side of said generating means.

1. In a generating system comprising a generating machine including afield circuit comprising a field winding and electrical connections forconnecting a battery to be charged by said generating machine to saidmachine, said connections including switching means having first andsecond conditions for respectively electrically connecting anddisconnecting said generating machine to and from said battery, saidswitching means requiring a predetermined electrical signal foractuation from its first condition to its second condition, second meansfor providing said electrical signal when said generating machine isgenerating an output comprising a transformer having a primary windingconnected to said generating machine to be energized with a currentwhich changes in a pulsing manner when said generating machine isoperating and a secondary winding connected to said switching means toprovide said predetermined signal in response to a predetermined pulsingchange in said current, and third means responsive to reverse batterypolarity for saturating said transformer to prevent current in saidprimary winding from inducing currents in said secondary winding toprovide said predetermined signal.
 2. In a generating system as definedin claim 1 wherein said generating machine is a machine which generatesa direct current.
 3. In a generating system as defined in claim 16wherein said primary winding is connected into the field circuit of saidgenerating machine.
 4. In a generating system as defined in claim 3wherein said switching means is a controlled rectifier and saidsecondary winding is connected to provide gate signals to saidrectifier.
 5. In a generating system as defined in claim 3 wherein saidsystem includes a voltage regulator for regulating the output of saidgenerating machine by controlling the current in said field winding inresponse to said output, said regulating means switching off and on asthe output of said generating machine rises and falls to predeterminedlevels to provide said current which pulses in a predetermined manner.6. In a generating system as defined in claim 4 wherein said systemincludes a voltage regulator for regulating the output of saidgenerating machine by controlling the current in said field winding inresponse to said output, said regulating means switching off and on asthe output of said generating machine rises and falls to predeterminedlevels to provide said current which pulses in a predetermined manner.7. In a generating system as defined in claim 1 wherein said third meanscomprises a saturating winding for said transformer and circuit meansconnecting said saturating winding across the battery terminals of saidbattery, said circuit means including uni-directional conducting meansfor blocking current flow in said saturating winding when said batteryis connected to the battery terminals with proper polarity and wherebysaid circuit means is conductive when said battery is inserted withreverse polarity to saturate said transformer.
 8. In a generating systemas defined in claim 7 wherein said switching means is a controlledrectifier and said secondary winding is connected to provide gatesignals to said rectifier.
 9. In a generating system as defined in claim7 wherein said machine is a generating machine for generating a directcurrent and said primary winding is connected into the field circuit ofsaid generating machine.
 10. In a generating system as defined in claim9 wherein said switching means is a controlled rectifier and saidsecondary winding is connected to provide gate signals to saidrectifier.
 11. In a generating system as defined in claim 9 wherein Saidgenerating system includes voltage regulating machine responsive to theoutput of said generating means for controlling the field current insaid field winding, said voltage regulating means switching said fieldcurrent off and on as the output of said generating machine rises andfalls to predetermined levels to provide said current which pulses in apredetermined manner.
 12. In a generating system, generating means to beconnected to supply direct current to charge a battery, said generatingmeans having a field circuit comprising a field winding, load conductorsconnecting the output of said generating means to said battery,switching means in said load conductors for connecting and disconnectingthe output of said generating means to and from said battery, means forsensing current in said field circuit, and means responsive to the lastsaid means for supplying a signal to said switching means to activatethe latter to connect the generating means to said battery when thegenerating means has started.
 13. In a generating system as defined inclaim 12 wherein said means for sensing current in said field circuitcomprises a circuit element connected in series with said field winding.14. In a generating system as defined in claim 12 in which saidgenerating system includes means responsive to the polarity of saidbattery for inhibiting the activation of said switching means inresponse to said means for sensing current in said field.
 15. In agenerating system as defined in claim 14 wherein said switching meanscomprises a controlled rectifier having its anode connected to thepositive side of said generating means.